The present invention relates to a centrifugal separator having a cooling device, and more particularly, to the centrifugal separator capable of discharging dew condensation water which remain in a rotor room, at a time of cooling, to an exterior of the rotor room with high efficiency.
The centrifugal separator conducts separation or purification of a sample, by inserting the sample to be separated (incubating liquid, blood, for example) into a rotor by means of a tube or a bottle, and by rotating the rotor at a high speed. Set rotation speed of the rotor is different depending on objects for use. According to the objects for use, there are provided groups of products having the rotation speeds from a low speed (about several thousand rotations) to a high speed (the highest rotation speed is 150,000 rpm). Various types of rotors including, for example, an angle rotor having a tube hole of a fixed angle type and operable at the high rotation speed, a swing rotor in which a bucket loaded with a tube is swung from a vertical state to a horizontal state following rotation of the rotor, and so on are used. Moreover, there are rotors having various sizes including, for example, a rotor which is rotated at an ultrahigh rotation speed to apply high centrifugal acceleration to a small amount of sample, and a rotor which is rotated at a low rotation speed, but can deal with a large capacity of sample.
Some of the rotors should be kept at a low temperature depending on the sample. However, when the rotor holding the sample is rotated at a high speed in the atmosphere, the temperature tends to rise due to frictional heat occurring between an outer surface of the rotor and the air inside the rotor room. For this reason, a cooling device is mounted on many types of centrifugal separators so that the sample can be cooled and kept at a certain temperature. In the centrifugal separator having such a cooling device, in case where a door is opened after the centrifuging operation to expose the rotor room to an outside air, condensation occurs on a side wall of the rotor room, in some cases. As a countermeasure, as disclosed in Japanese Utility Model Publication No. JP-B-S52-42445U and Japanese Patent Publication No. JP-A-2006-346617, the centrifugal separator is so constructed that a drain hole is formed in a bottom part of a chamber which defines the rotor room, and dew condensation water which has been generated is discharged from the drain hole through a drain pipe to the exterior.
Herein, a structure of the related centrifugal separator will be described referring to FIG. 8. FIG. 8 is a vertical sectional view of a related centrifugal separator 101, in which a rotor room 105 is defined by a chamber 106, and a rotor 2 in the rotor room 105 is driven to rotate by a driving device 11. A refrigerating pipe 18 is wound around the chamber 106. An outlet side of the refrigerating pipe 18 is connected to a compressor 17 a, and an outlet side of the compressor 17 a is connected to a condenser 17 b via a pipe. An outlet side of the condenser 17 b is connected to the refrigerating pipe 18 via a throttle mechanism, which is not shown. The refrigerating pipe 18, compressor 17 a, condenser 17 b, throttle mechanism, and so on constitute a cooling device, which effectively cools the chamber 106 by passing a refrigerant through the refrigerating pipe 18. In this manner, by cooling the chamber 106 during the centrifuging operation, the temperature rise of the rotor 2 due to frictional heat which is generated between an outer surface of the rotor 2 and an air inside the rotor room 105 is depressed.
In order to keep the rotor 2 at a desired low temperature, for example, 4° C., the chamber 106 should be cooled to almost 0° C. However, when a door 7 is opened in a thus cooled state, immediately after the operation has stopped, an outside air intrudes into the rotor room 105, and water contained in the outside air is condensed on inner and outer surfaces of the chamber 106, to generate dew condensation water, in some cases. The dew condensation water which has been generated falls along a wall surface of the chamber 106 and remains in a bottom part of the chamber 106. When the dew condensation water remains inside the rotor room 105, an airflow which is generated inside the rotor room 105 is hindered by the dew condensation water, during rotation of the rotor 2, and resistance of the driving device 11 for driving the rotor 2 to rotate is inevitably increased. Moreover, there is such anxiety that the dew condensation water swirls together with the airflow which is generated in the rotor room 105 to enter into the sample, or to enter into a bucket 3.
Therefore, in the centrifugal separator which is disclosed in Japanese Patent Publication No. JP-A-2006-346617, a drain hole 113 is formed in the bottom part of the chamber 106, and the generated dew condensation water are allowed to flow from the drain hole 113 to a drain pipe 114 to be discharged to an exterior of the centrifugal separator 101 through a drain tube 115. The dew condensation water which remains in the rotor room 105 is affected by a flow of the air which is generated in the rotor room 105 during the rotation of the rotor 2, and spirally flows toward a center of a rotation shaft of the driving device 11, while winding around the rotation shaft of the driving device 11 in the bottom part of the chamber 106. A riser part 109 a in a cylindrical shape is provided in the bottom part of the chamber 106 so as to rise substantially vertically, and therefore, the dew condensation water is concentrated around the riser part 109 a to flow along an outer periphery of the riser part 109 a in the same direction as a rotation direction of the rotor 2 in such a manner as sticking to the riser part 109 a. The riser part 109 a is integrally formed with a seal rubber 109 which is fitted to an outer peripheral surface of the driving device 11. The drain pipe 114 is connected to the drain hole 113, and the flow of the dew condensation water which is generated with the rotation of the rotor 2 in the bottom part of the chamber 106 is guided to the drain pipe 114 to be discharged to the exterior of the centrifugal separator with high efficiency.
However, in the related structure, in case where speed of the airflow is high due to a high rotation of the rotor 2, or in case where an amount of the dew condensation water is large, it has sometimes occurred that while the dew condensation water flows around the riser part 109 a, a part of the dew condensation water overrides the riser part 109 a to arrive at a flat surface 109 b of the seal rubber 109 which covers an opening at an upper end of the riser part 109 a, and spirally flows along the flat surface 109 b toward the rotation center of the driving device. When the dew condensation water has arrived at the flat surface 109 a of the seal rubber 109 as described above, the dew condensation water is influenced by the airflow which is generated with the rotation of the rotor 2, and it becomes difficult to discharge the dew condensation water from the drain hole 113 which is opened at an outer peripheral side of the riser part 109 a, during the rotation of the rotor 2.
As a countermeasure, it is considered that a height of the riser part 109 a is made sufficiently high so that the dew condensation water may not override the riser part 109 a, even in a state where the speed of the airflow is high or the amount of the dew condensation water is large. However, in order to make the height of the riser part 109 a high, the chamber 106 should be made higher, and accordingly, a height of the centrifugal separator 101 itself becomes inevitably high, which badly affects usability of a user.